1. Field of the Invention
The invention relates to the field of digital communication protocols and circuits, and in particular to phase modulation communication protocols and circuits using only the carrier frequency, without sidebands, for information transmittal or reception.
2. Description of the Prior Art
Ultra Narrow Band Methods must separate the carrier from the sidebands, transmitting only one or the other. The object is to obtain a single modulation bearing frequency, or very narrow band of frequencies, that will occupy the least possible transmitted bandwidth. U.S. Pat. Nos. 4,742,532, 5,185,765 and 5,930,303 encode the data stream, then transmit the resulting waveform as a “Single Sideband—Suppressed Carrier—Phase Modulated” signal.
U.S. Pat. No. 6,445,737 modifies the carrier as little as possible and transmits a signal in which the sidebands are suppressed or ignored. In the prior art, other than that described in the references above, every effort is made to use phase shift modulation in a continuous, or smooth phase changing manner, as opposed to the abrupt change manner of the present invention. This prior art has resulted in a modulation concept known as Continuous Phase Frequency Shift Keying (CPFSK), which applies to all the commonly used methods. The CPFSK method results in frequency as well as phase modulation, with the required J0 and J1 Bessel products.